Field of the Invention
The present invention relates to a method of manufacturing a magnetic recording medium, a magnetic recording medium, and a magnetic recording and reproducing apparatus.
Priority is claimed on Japanese Patent Application No. 2013-010088, filed on Jan. 23, 2013 and Japanese Patent Application No. 2014-007216, filed on Jan. 17, 2014 the content of which is incorporated herein by reference.
Description of Related Art
A hard disk drive (HDD), which is a kind of a magnetic recording and reproducing apparatus, currently shows an annual growth rate of 50% or higher in its recording density, which is expected to continue in the future. According to this trend, a magnetic head and a magnetic recording medium suitable for high recording density have been developed.
A magnetic recording and reproducing apparatus that is currently available on the market is mounted with a perpendicular magnetic recording medium in which an easy axis of magnetization in a magnetic film is mainly perpendicularly orientated, as a magnetic recording medium. In the perpendicular magnetic recording medium, since the influence due to an inverse magnetic field in a boundary region between recording bits is small and a clear bit boundary is formed, even in high recording density, a noise increase is suppressed. In addition, in the perpendicular magnetic recording medium, since a decrease in a recording bit volume associated with high recording density is small, a thermal fluctuation characteristic is excellent.
Further, in order to meet the demand for higher recording density of the magnetic recording medium, a single magnetic pole head having excellent writing performance with respect to a perpendicular magnetic layer has been studied for use. Specifically, a magnetic recording medium has been proposed in which a layer formed of a soft magnetic material, a so-called backing layer, is provided between a perpendicular magnetic layer that is a recording layer and a non-magnetic substrate to improve magnetic flux entering/exiting efficiency between the single magnetic pole head and the magnetic recording medium.
Further, in order to improve the recording and reproducing characteristic and the thermal fluctuation characteristic of the perpendicular magnetic recording medium, a method of forming plural magnetic layers using an orientation control layer and forming a crystal grain of each magnetic layer as a continuous columnar crystal to improve vertical orientation of the magnetic layer has been proposed (for example, see Japanese Unexamined Patent Application, First Publication No. 2004-310910).
Further, Japanese Unexamined Patent Application, First Publication No. H07-244831 discloses a method of providing a crystal orientation-facilitating layer on a substrate in advance, and sputter-depositing a perpendicular magnetic anisotropic thin film through the crystal orientation-facilitating layer at a sputtering gas pressure of 10 Pa or higher.
Furthermore, a technique in which Ru is used as the orientation control layer has been proposed (For example, see Japanese Unexamined Patent Application, First Publication No. 2007-272990). It is known that Ru forms a dome-like convex part at the top of a columnar crystal. Thus, by growing a crystal grain of a magnetic layer or the like on the orientation control layer having the convex part, formed of Ru, it is possible to accelerate a separation structure of the grown crystal grains and to isolate the crystal grains. Thus, an effect of growing magnetic particles in a columnar shape is obtained.
Further, a magnetic recording medium in which a ruthenium-containing layer formed at a low pressure argon atmosphere (0.6 Pa), a ruthenium-containing layer formed at a high pressure argon atmosphere (10 Pa) and a perpendicular magnetic layer are sequentially formed on a substrate has been proposed (see Japanese Unexamined Patent Application, First Publication No. 2002-197630). As the Ru layer is formed at a high sputtering pressure on the Ru layer formed at a low sputtering pressure, it is possible to improve the orientation of the Ru layer, to improve the orientation of the perpendicular magnetic layer grown thereon, and to miniaturize magnetic particles.
Further, PCT International Publication No. WO2010/035810 discloses a technique in which an Ru layer is formed at a high gas pressure on an Ru layer formed at a low gas pressure and Co and oxygen are included in the Ru layer formed at the high gas pressure, to miniaturize crystal grains of the Ru layer formed at the high gas pressure. Further, in PCT International Publication No. WO2010/035810, as an oxide included in the granular layer, SiO2, TiO2 or Cr2O3 is used, for example.